Layer-by-layer assembled composites from multiwall carbon nanotubes with different morphologies

We report formation of polyelectrolyte/multiwall carbon nanotube (MWNT) multilayers; by the layer-by-layer assembly technique. Both hollow and bamboo type MWNTs were employed. Scanning electron and atomic force microscopy indicate high structural homogeneity of the prepared composites. Ellipsometry and the absorbance spectroscopy confirm sequential adsorption of oppositely charged nanotubes and the polyelectrolyte resulting in uniform growth of the polyelectrolyte/MWNT films. Measurements of the mechanical properties show that these are strong composite hybrid films with mechanical properties exceeding many carbon nanotube composites made by mixing, or in-situ polymerization. Bamboo-type carbon nanotube composites display ultimate tensile strength of 150 +/- 35 MPa and Young modulus of 4.5 +/- -0.8 GPa as compared to 110 +/- 25 MPa and 2 +/- 0.5 GPa in composites made from common hollow MWNTs. This indicates that the morphology of the fibers can substantially improve matrix connectivity on the material mitigating telescopic effect in MWNTs. The films made from bamboo-type MWNTs approach in strength recently reported layer-by layer composite films from single wall carbon nanotubes, while being substantially less expensive. These results confirm the potential of the layering method for the manufacturing of composites with high load of strong filler and importance of uniform distribution and good interconnectivity between carbon nanotubes and the polymer matrix.